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Four gunmen and two troops have been killed in an attack on an Indian Air Force base near the border with Pakistan, in an apparent challenge to attempts to revive a dialogue between the nuclear-armed neighbours.

Indian defence ministry sources said yesterday four gunmen, believed to be from Pakistan, had entered the Pathankot airbase in India's northwestern state of Punjab overnight.

Fresh gunfire was reported inside the base last night.

The attack came a week after Indian Prime Minister Narendra Modi made an impromptu visit to Pakistani counterpart Nawaz Sharif, to revive bilateral talks previously been derailed by militants.

"The moment Modi touched down in Lahore something like this was doomed to happen," said Michael Kugelman, a South Asia expert at the Wilson Centre think tank in Washington.

"At this point, there is sufficient goodwill in India-Pakistan relations to weather this attack. Saboteurs won't win this one," he said.

Border police chief Vijay Singh said the shootout lasted three hours. The airbase was being combed to find the remaining attackers.

News reports said the gunmen wore army uniforms. One Indian security source blamed the attack on a Pakistan-based militant group, but said it posed no threat to civilians.

The raid resembled an assault last July by gunmen on a police post in a Punjabi border town that killed nine people. However, yesterday's attack targeted a large military facility.

An Indian home ministry official said Punjab and Jammu states were on high alert and all defence bases had been sealed. "Attacking an air base is a serious security threat. The strategy of the terrorists is to [attack] defence bases near the border."